Hello everyone! How are you guys?

Im a Biomedic Student, and I must to read a lot of Scientifc Articles, for the better learning.

Well, what happens is that, I'm think I'm good for conversation in english, and sometimes even to write (like right now, but you can report me if I'm missing). BUT when we talk about the interpretion read, I'm a socks!

So, I've been trying to desenvolve a strategic way to interpretation when I reading, like, talking while I'm reading.

I know then someday it will be solved by my practicing, but, for the pratic, I first need a strategic. 

I've been used a Google Translation, but isn't ever then it can help me. 

Like a expression that I saw. It was:  "Upon exogenous challenges".

Well, I know what it means "exogenous" and "challenges", but I don't know where to fit in "upon" to make any sense, cause I don't know what means "upon" when it comes just that word whit itself. For exemple: I know what means "Once UPON a Time" (Era uma vez), but just "upon", I just don't know, and the google doesn't show me. 

Message me if you have a solution to my problem, or just for turn this text better for a english native interpretetion!

xoxo